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Subject[PATCH 26/31] x86: MCE: Export MCE severities coverage via debugfs
Date
From: Huang Ying <ying.huang@intel.com>

The MCE severity judgement code is data-driven, so code coverage tools such as
gcov can not be used for measuring coverage. Instead a dedicated coverage
mechanism is implemented. The kernel keeps track of rules executed
and reports them in debugfs.

This is useful for increasing coverage of the mce-test testsuite.

Right now it's unconditionally enabled because it's very little code.

Signed-off-by: Huang Ying <ying.huang@intel.com>
Signed-off-by: Andi Kleen <ak@linux.intel.com>
---
arch/x86/kernel/cpu/mcheck/mce-severity.c | 83 +++++++++++++++++++++++++++++
1 files changed, 83 insertions(+), 0 deletions(-)
diff --git a/arch/x86/kernel/cpu/mcheck/mce-severity.c b/arch/x86/kernel/cpu/mcheck/mce-severity.c
index 4f4d2ca..ff0807f 100644
--- a/arch/x86/kernel/cpu/mcheck/mce-severity.c
+++ b/arch/x86/kernel/cpu/mcheck/mce-severity.c
@@ -10,6 +10,9 @@
* Author: Andi Kleen
*/
#include <linux/kernel.h>
+#include <linux/seq_file.h>
+#include <linux/init.h>
+#include <linux/debugfs.h>
#include <asm/mce.h>

#include "mce-internal.h"
@@ -37,6 +40,7 @@ static struct severity {
unsigned char mcgres;
unsigned char ser;
unsigned char context;
+ unsigned char covered;
char *msg;
} severities[] = {
#define KERNEL .context = IN_KERNEL
@@ -126,6 +130,7 @@ int mce_severity(struct mce *a, int tolerant, char **msg)
continue;
if (msg)
*msg = s->msg;
+ s->covered = 1;
if (s->sev >= MCE_UC_SEVERITY && ctx == IN_KERNEL) {
if (panic_on_oops || tolerant < 1)
return MCE_PANIC_SEVERITY;
@@ -133,3 +138,81 @@ int mce_severity(struct mce *a, int tolerant, char **msg)
return s->sev;
}
}
+
+static void *s_start(struct seq_file *f, loff_t *pos)
+{
+ if (*pos >= ARRAY_SIZE(severities))
+ return NULL;
+ return &severities[*pos];
+}
+
+static void *s_next(struct seq_file *f, void *data, loff_t *pos)
+{
+ if (++(*pos) >= ARRAY_SIZE(severities))
+ return NULL;
+ return &severities[*pos];
+}
+
+static void s_stop(struct seq_file *f, void *data)
+{
+}
+
+static int s_show(struct seq_file *f, void *data)
+{
+ struct severity *ser = data;
+ seq_printf(f, "%d\t%s\n", ser->covered, ser->msg);
+ return 0;
+}
+
+static const struct seq_operations severities_seq_ops = {
+ .start = s_start,
+ .next = s_next,
+ .stop = s_stop,
+ .show = s_show,
+};
+
+static int severities_coverage_open(struct inode *inode, struct file *file)
+{
+ return seq_open(file, &severities_seq_ops);
+}
+
+static ssize_t severities_coverage_write(struct file *file,
+ const char __user *ubuf,
+ size_t count, loff_t *ppos)
+{
+ int i;
+ for (i = 0; i < ARRAY_SIZE(severities); i++)
+ severities[i].covered = 0;
+ return count;
+}
+
+static const struct file_operations severities_coverage_fops = {
+ .open = severities_coverage_open,
+ .release = seq_release,
+ .read = seq_read,
+ .write = severities_coverage_write,
+};
+
+static int __init severities_debugfs_init(void)
+{
+ struct dentry *dmce = NULL, *fseverities_coverage = NULL;
+
+ dmce = debugfs_create_dir("mce", NULL);
+ if (dmce == NULL)
+ goto err_out;
+ fseverities_coverage = debugfs_create_file("severities-coverage",
+ 0444, dmce, NULL,
+ &severities_coverage_fops);
+ if (fseverities_coverage == NULL)
+ goto err_out;
+
+ return 0;
+
+err_out:
+ if (fseverities_coverage)
+ debugfs_remove(fseverities_coverage);
+ if (dmce)
+ debugfs_remove(dmce);
+ return -ENOMEM;
+}
+late_initcall(severities_debugfs_init);
--
1.6.0.2


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